Secondary batteries using a non-aqueous electrolyte solution are widely used as power sources for consumer electronic devices because such batteries have high voltage, high energy density, and high reliability of storage characteristics or the like. Secondary batteries using a non-aqueous electrolyte solution are beginning to be used also as batteries for electric power storage, and automobiles such as electric vehicles (EVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs). Representative examples of secondary batteries using a non-aqueous electrolyte solution include lithium batteries and lithium ion secondary batteries.
The non-aqueous electrolyte solution used in such secondary batteries is a solution obtained by mixing an electrolyte into a non-aqueous solvent, and the electrolyte contained in the non-aqueous electrolyte solution transfers ions between a positive electrode and a negative electrode. The non-aqueous electrolyte solution is demanded to have the following characteristics in order to enhance battery performance of secondary batteries.
First, the non-aqueous electrolyte solution needs to be chemically and electrochemically stable with respect to the positive electrode and the negative electrode in order to improve the storage characteristics and cycle characteristics of secondary batteries.
In order to enhance the charge and discharge characteristics of secondary batteries, the non-aqueous electrolyte solution is preferably a liquid having a high ion movement speed, and specifically, is demanded to have a low viscosity and to be a liquid that readily causes mass transfer by diffusion.
It is known that a carbonate solvent having a high dielectric constant such as propylene carbonate or ethylene carbonate, or a carbonate solvent with low viscosity such as diethyl carbonate, ethyl methyl carbonate, or dimethyl carbonate is used as the non-aqueous solvent of the non-aqueous electrolyte solution in order to satisfy the above characteristics needed for the non-aqueous electrolyte solution. Further, it is known that a boron compound is added to a non-aqueous electrolyte solution to improve battery performance such as storage characteristics, cycle characteristics, or charge and discharge characteristics of a secondary battery (for example, Patent Documents 1 to 10).
Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. H09-120825
Patent Document 2: JP-A No. H10-223258
Patent Document 3: JP-A No. H11-054133
Patent Document 4: JP-A No. H11-121033
Patent Document 5: JP-A No. 2002-025609
Patent Document 6: JP-A No. 2002-216844
Patent Document 7: JP-A No. 2003-132946
Patent Document 8: JP-A No. 2003-168476
Patent Document 9: JP-A No. 2008-198542
Patent Document 10: JP-A No. 2009-245829